Placeholder images in docs no longer work

[trichoplax]

Describe the bug
In the docs on https://design.codidact.org/components/item-lists/ there are placeholder images provided by a third party service https://placekitten.com that is no longer working.

To Reproduce
Steps to reproduce the behavior:

1. Go to https://design.codidact.org/components/item-lists/
2. Scroll to the bottom of the page
3. See alt text "placeholder image" instead of placeholder images on the right hand side of the example questions

Expected behavior
Placeholder images should show instead of the alt text.

Can we either host placeholder images locally or find a replacement source?